The disclosure relates generally to sampling analog-to-digital converters (ADCs), and more particularly to providing devices, systems, and methods, including in distributed antenna systems (DASs), to simultaneously sample ADCs.
An ADC converts an analog input signal into a digital output signal. The digital output signal is a digital representation or value of the analog input signal. For example, for an 8-bit ADC having a digital output signal range of 0-255 (i.e., 0xFF), an analog signal having an amplitude of the maximum range of the ADC would be converted to the digital value 255. This conversion takes a specific amount of time for the ADC to complete, depending on such factors as the method used by the ADC for the conversion, the desired level of precision, and the signal processing capabilities of the ADC. ADCs can be deployed in systems, including communications systems that carry analog communications signals, to convert analog signals to digital values for further processing and analysis in a digital domain.
A DAS is a type of communications system that may distribute analog communications signals. In a DAS, communications signals can be distributed from a central unit (which can also be referred to as a head-end unit) to one or more remote units forming remote coverage areas. ADCs may be provided in communications components in a DAS to sample distributed communications signals or to convert detected information about the distributed communications signals, such as radio frequency (RF) power, from an analog value to a digital value for analysis and processing. In this regard, FIG. 1 illustrates an exemplary DAS 10 that can include ADCs 12(1)-12(N) (only one ADC, 12(1) is shown) to convert analog signals distributed in the DAS 10 to digital values. The DAS 10 provides distribution of communications signals to provide communications services to coverage areas 14(1)-14(N) in the DAS 10, where N is the number of coverage areas. These communications services can include cellular services, such as a cellular service operating using the Long Term Evolution (LTE) cellular protocol, for example. The coverage areas 14(1)-14(N) may be remotely located. In this case, the remote coverage areas 14(1)-14(N) are created by and centered on remote antenna units 16(1)-16(N) coupled to a central unit 18 (e.g., a head-end controller or head-end unit). The central unit 18 may be communicatively coupled to a base station 20. In this regard, the central unit 18 receives analog downlink communications signals 22D from the base station 20 to be distributed to the remote antenna units 16(1)-16(N). The remote antenna units 16(1)-16(N) are configured to receive the downlink communications signals 22D from the central unit 18 over a communications medium 24 to be distributed to the respective coverage areas 14(1)-14(N) of the remote antenna units 16(1)-16(N). Each remote antenna unit 16(1)-16(N) may include one or more RF transmitters/receivers (not shown) and respective antennas 26(1)-26(N) operably coupled to the RF transmitters/receivers to wirelessly distribute the communications services to client devices 28 within their respective coverage areas 14(1)-14(N). The remote antenna units 16(1)-16(N) are also configured to receive analog uplink communications signals 22U from the client devices 28 in their respective coverage areas 14(1)-14(N) to be distributed to the base station 20.
It may be desired to determine information regarding the downlink communications signals 22D and/or the uplink communications signals 22U distributed in the DAS 10 for diagnostic or operational reasons. For example, it may be desired to determine the RF power level of the downlink and/or the uplink communications signals 22D, 22U. The RF power levels may be used to calibrate gain levels in the DAS 10 or determine if any communications component is not distributing a downlink and/or an uplink communications signal 22D, 22U with the proper gain. In this regard, power detectors 30(1)-30(N) (only one power detector, 30(1) is shown) can be provided at specific points in the DAS 10. The power detectors 30(1)-30(N) each provide a respective output signal 32(1)-32(N) (only one output signal, 32(1) is shown) indicative of the RF power in a downlink and/or an uplink communications signal 22D, 22U at such point or location. The output signals indicative of RF power generated by the power detectors 30(1)-30(N) are also typically analog signals. However, it may be desired to process these output signals in a digital domain, such as in a microcontroller unit (MCU) 34 shown in FIG. 1. Thus, the ADCs 12(1)-12(N) are employed in FIG. 1 to convert the analog output signals 32(1)-32(N) generated by the power detectors 30(1)-30(N) to respective digital data streams 36(1)-36(N) (only one digital data stream, 36(1) is shown). The MCU 34 may then perform processing, including inter-sample processing (e.g., calculating average power of every stream), of the digital data streams 36(1)-36(N) collected from the multiple ADCs 12(1)-12(N) at multiple locations in the DAS 10.
As the desire to obtain more information about downlink and/or uplink communications signals 22D, 22U in different frequency bands or points in the DAS 10 increases, the number of ADCs 12(1)-12(N) provided in the DAS 10 increases. Thus, the MCU 34 must sample an increased number of digital data streams 36(1)-36(N) from the ADCs 12(1)-12(N), which consumes an increasing percentage of the resources of the MCU 34. This increase in resources consumed by sampling the ADCs 12(1)-12(N) leads to fewer resources available for other tasks the MCU 34 must perform.
Several solutions to this problem of decreased MCU 34 availability exist. First, an MCU 34 with increased signal processing capabilities can be used. This may also require that the ADCs 12(1)-12(N) have increased signal processing capabilities. Providing an MCU 34 and ADCs 12(1)-12(N) in the DAS 10 with increased processing capabilities may be more expensive than providing less expensive MCU and ADCs with reduced processing capabilities. Second, an additional MCU 34 may be provided in the DAS 10 that is dedicated to sampling the ADCs 12(1)-12(N) within the required time.
No admission is made that any reference cited herein constitutes prior art. Applicant expressly reserves the right to challenge the accuracy and pertinence of any cited documents.